package org.argeo.jcr;


/**
 * Simple monitor abstraction. Inspired by Eclipse IProgressMOnitor, but without
 * dependency to it.
 */
public interface JcrMonitor {
	/**
	 * Constant indicating an unknown amount of work.
	 */
	public final static int UNKNOWN = -1;

	/**
	 * Notifies that the main task is beginning. This must only be called once
	 * on a given progress monitor instance.
	 * 
	 * @param name
	 *            the name (or description) of the main task
	 * @param totalWork
	 *            the total number of work units into which the main task is
	 *            been subdivided. If the value is <code>UNKNOWN</code> the
	 *            implementation is free to indicate progress in a way which
	 *            doesn't require the total number of work units in advance.
	 */
	public void beginTask(String name, int totalWork);

	/**
	 * Notifies that the work is done; that is, either the main task is
	 * completed or the user canceled it. This method may be called more than
	 * once (implementations should be prepared to handle this case).
	 */
	public void done();

	/**
	 * Returns whether cancelation of current operation has been requested.
	 * Long-running operations should poll to see if cancelation has been
	 * requested.
	 * 
	 * @return <code>true</code> if cancellation has been requested, and
	 *         <code>false</code> otherwise
	 * @see #setCanceled(boolean)
	 */
	public boolean isCanceled();

	/**
	 * Sets the cancel state to the given value.
	 * 
	 * @param value
	 *            <code>true</code> indicates that cancelation has been
	 *            requested (but not necessarily acknowledged);
	 *            <code>false</code> clears this flag
	 * @see #isCanceled()
	 */
	public void setCanceled(boolean value);

	/**
	 * Sets the task name to the given value. This method is used to restore the
	 * task label after a nested operation was executed. Normally there is no
	 * need for clients to call this method.
	 * 
	 * @param name
	 *            the name (or description) of the main task
	 * @see #beginTask(java.lang.String, int)
	 */
	public void setTaskName(String name);

	/**
	 * Notifies that a subtask of the main task is beginning. Subtasks are
	 * optional; the main task might not have subtasks.
	 * 
	 * @param name
	 *            the name (or description) of the subtask
	 */
	public void subTask(String name);

	/**
	 * Notifies that a given number of work unit of the main task has been
	 * completed. Note that this amount represents an installment, as opposed to
	 * a cumulative amount of work done to date.
	 * 
	 * @param work
	 *            a non-negative number of work units just completed
	 */
	public void worked(int work);

}